Weak Tuner?
I have two DVRs. I have A Channels DVR setup with two Silicon Dust tuners ( HD Homerun Connect and a Connect Quatro)
I also own a Tablo TV dvr.
The outside antenna goes through an amplified 4 way splitter on the mast. One lead goes to the Tablo, One goes to the Quatro and one goes to the Connect and the last one goes into a TV in the bedroom.
The Tablo allows me top see the signal strength of all the stations that I have on it (and thus the strength of the signal going to the HDHomeruns.)
On the Tablo the NBC affiliate (11.10) comes in with 5 out of 5 bars as does the ION affiliate (14.1).
On setting up my Channels DVR the DVR saw both stations but neither one of the Silicon Dust units could receive either station.
The Tablo on the other hand brings them in extremely well.
The HDHomeruns do bring in some stations that only have 4 bars. And they don't seem to have a problem with the ABC or FOX stations that also pull in 5 bars.
I think that it must have something other than signal strength but I have no ideas at this point.
Any help or suggestion would be appreciated.

Actually that sounds like the classic signal strength issue that has been discussed here many times. Not that the signal to the HDHRs is too weak but that it's too strong. That's especially common when an amplifier is in the line. Your strongest channels don't work but the weaker ones do.

If you have a passive splitter, try putting it in the line currently going to one HDHR and feed both HDHRs from its outputs. That will drop the signal to each HDHR about 3.5 dB for a 2-output splitter or 7 dB for a 4-output one (you should terminate any unused outputs). That may improve reception of the strongest stations. Also check whether you can still get the weakest ones.

Standard Windows installations have a strength/quality meter program called hdhomerun_config_gui.exe in the program directory. Linux and (I believe) Mac have similar ones. You should reduce the strongest signals to a little below 100% because if it says 100% you don't know how much stronger it might be.